(a) Field of the Invention
This invention relates to a microscope optical system wherein a Jentzch type binocular system is used and more particularly to a microscope optical system wherein both observation and photographing can be made and, in the case of the photographing, a binocular optical system can be used as a view finder.
(b) Description of the Prior Art
FIG. 1 shows an optical system of a microscope wherein a conventional Jentzch type binocular optical system (formed of a Jentzch type prism, eyepiece and others) is used. In the formation of this kind of microscope, both observation and photographing can be made and, in the case of the photographing, the binocular optical system can be used as a view finder. That is to say, in FIG. 1, the reference numeral 1 denotes an objective, 2 denotes a relay lens, 3 denotes a reflecting prism for bending an optical axis, 4 denotes a projecting lens, 5 denotes a quick-return mirror, 6 denotes a film, 7 denotes a reflecting mirror, 8 denotes a relay lens, 9 denotes a reflecting prism for bending an optical axis, 10 denotes an observing direction changing prism, 11 denotes a Jentzch type binocular prism and 12 denotes an eyepiece. In this optical system, at the time of the observation, the reflecting prism 3 will be placed outside the light path, the light from the object will pass through the objective 1 and relay lens 2, will be reflected by the reflecting prism 9 and will enter the observing direction changing prism 10 and Jentzch type binocular prism 11. As shown in FIG. 2, this Jentzch type binocular prism 11 consists of a beam splitter 13 and binocular prisms 14 and 14'. Therefore, the light coming out of the observing direction changing prism 10 will enter the beam splitter 13 of the Jentzch type prism 11 and will be partly reflected and partly passed by its dividing surface 13a.The light reflected by the dividing surface 13a of the beam splitter 13 will come out of the side of the beam splitter 13, will enter the binocular prism 14', will be reflected by its reflecting surface, will be directed in the direction substantially parallel with the axis of the light entering the beam splitter 13 and will come out of the prism 14'. The light having passed through the dividing surface 13a of the beam splitter 13 will be reflected by the reflecting surface in front of the dividing surface, will be bent by substantially 90 degrees, will be projected out of the side surface of the beam splitter, will enter the binocular prism 14, will be reflected by its reflecting surface, will be directed in the direction substantially parallel with the axis of the light entering the beam splitter 13 and will be projected out of the prism 14. Therefore, the optical axes of the lights projected out of the binocular prisms 14 and 14' will be parallel with each other. Thus, the lights coming out of the binocular prisms 14 and 14' will be directed to be eyepiece 12 and the object image will be observed through the eyepiece 12. On the other hand, at the time of the photographing, when the reflecting prism 3 is inserted and the reflecting prism 9 is removed out of the light path, the light from the object will pass through the objective 1 and relay 2, will be reflected by the reflecting prism 3, will pass through the projecting lens 4, will be reflected by the quick-return mirror 5 and reflecting mirror 7, will be relayed by the relay lens 8 and will pass through the observing direction changing prisms 10 and Jentzch type prism 11, the object image will be observed through the eyepiece 12 and the eyepiece 12 will be used as a view finder. Here, if the quick-return mirror 5 is quickly turned to the chain line position, the image of the object will be formed on the film 6 and will be photographed.
In such conventional optical system as in the above, in the case of either of the observation and photographing, the light will be made to enter the binocular prism 11 (Jentzch type prism) through the observing direction changing prism 10 and therefore, there are so many surfaces by which the light is reflected that there have been defects that the picture quality is deteriorated by the light amount reduction and ghosts and that the assembly is difficult. Further, as the relay lens 2 is required, the formation will be complicated. As two prisms (or reflecting mirrors) must be arranged in the rear of the relay lens 2, the space for the arrangement will be necessary and the entire size will be large. Further, in case the magnification .beta..sub.2 of the relay lens 2 is .beta..sub.2 &gt;1, the prism and others arranged in the rear of the relay lens 2 will have to be made larger and therefore the size will be larger.